This disclosure is directed to an improved process which removes residual salts, catalytic materials and particles of polymer that have solidified from a stream of phenolic epoxy novolac or phenolic derivative epoxy resin intermediates or a mixture with methyl isobutyl ketone. In the method of manufacture of large quantities of such resins, the process involves intimate contact with chloride ions. It also involves intimate contact with dispersed particulate catalytic materials. The process is intended to make the intermediate, meaning the epoxy resin in a solvent. Such a process provides a quality rsin intermediate, but the quality of this intermediate is degraded by dispersed residual salt ions (in particular chloride ions), catalytic particles and solidified polymer flowing in the intermediate stream. Ideally, the stream is primarily the resin flowing with a solvent. It is desirable to remove the residual salts and especially the chloride ions, catalytic particles and solid polymer particles. By one approach, a coalescer can be used to separate impurities. Coalescers known heretofore have operated primarily as a mechanical filter utilizing a filter element to remove the impurities. Filters tend to clog, causing plugging and channeling through the filter material. It is believed that the purification process described hereinbelow yields a more consistent and high quality, low impurity product stream over a wide range of impurity concentrations. It is not as susceptible to plugging and channeling typical of packed fiber mechanical style coalescing devices.
Another problem which may occur in a coalescent device is the accumulation of emulsion forming a floc separating from the product stream. In other instances, there may be a rag layer having a relatively high surface tension formed on the liquid level interface. Moreover, such irregularities floating on the surface of a liquid body makes emulsion separation more difficult. This difficulty is in part overcome by introducing a mixed phase flow into an electrostatic coalescer utilizing an electrical field and thereby separating the emulsion into separate phases. This is distinctly desirable in contrast with the mechanical coalescer packed with filter fibers. In other words, the electrostatic coalescing process disclosed herein will operate over a wider range of feed impurities and will remove a wide range of impurities in the intermediate resin stream.
Electrostatic separation is very difficult to accomplish in view of the fact the solvent is normally conductive, perhaps highly conductive. The solvent can be selected to reduce conductivity somewhat; however, the conductivity is normally increased by the ubiquitous nature of the chloride ion. Even further, the chloride cation is typically sodium or potassium, normally a conductive cation.